C38 Redux

[JBLOG]

Is anyone aware of any tweaks/rework of the System 030 (D130;075). Yes, the N2600 crossover was reconfigured in the N2400 with a few resistors to reduce the possibility of overdriving the 075. Without changing the cabinet or drivers, is there any experience with different crossover designs, shelf-filters or zobel networks.

I found this suggestion on another forum and found it very interesting.

"...However, the low bass of a D130 in a vented box can be assisted somewhat, by using a "shelf filter" on the woofer, between the crossover and woofer... something like a 10mh choke and a 6 ohm high-wattage resistor (50 watts, use two 25 watt 12 ohm resistors in parallel) in parallel, wired in series with the woofer should make the power balance more palatable. Depending on the box baffle dimensions and such, some experimentation may be required, to tune this in for optimal balance and response flatness... but the above values, should be a good starting ballpark. If you do this, you may also have to add some padding to the tweeter... about a 3 ohm resistor in series, followed by a 25 ohm resistor to ground, between the crossover and tweeter, should re-balance things. Worth trying, might also be about a .33uf cap, in PARALLEL with the 3 ohm resistor... this will 'ramp up" the falling response response of the 075 above 15kHz, a couple dB, which will help the "air" of the tweeter. The shelving will reduce the system sensitivity from 100 to about 97 dB... but it'll give usable, full bass down to around 40 Hz."

[Baron030]

Hi JBLOG



Suggestion on another forum...
However, the low bass of a D130 in a vented box can be assisted somewhat, by using a "shelf filter" on the woofer, between the crossover and woofer... something like a 10mh choke and a 6 ohm high-wattage resistor (50 watts, use two 25 watt 12 ohm resistors in parallel) in parallel, wired in series with the woofer should make the power balance more palatable.


The shelf filter is really a bad idea. The insertion losses are really excessive ranging from -3.2 db to -4.9 db depending on the frequency. So, this "shelf filter" only gives you a 1.7 db boost of bass, at the cost of -4.9db in gain. Or to put it another way, out of 60 watts coming from an amplifier, 26 watts does nothing more that heat up a resistor and the remaining 34 watts goes to the D130.

A much simpler and better solution would be to turn up the "Bass" knob on the pre-amplifier a little. Or you could place the speakers in the corners of the room, as this will also give the bass a boost.

Baron030 :)

[BMWCCA]

Probably why I've been a near-life-long user of Soundcraftsmen EQ/preamps almost all my years living with the 030s. I did fry an 075 once, but JBL fixed it for free (remember the "Lifetime" warranty?) and pointed me to my (Kenwood) receiver for "high-frequency oscillations. It's been PE2217 and DX4200s ever since! Well, at least after I retired the McIntosh C20, but then it has that variable loudness control....probably help with that LSR32 problem on the other forum, too!
:blink:

[JBLOG]

Thanks for the practical solutions....don't want to waste watts on heat!

[BMWCCA]

I think I understand what you tried to say. :blink:
With a DC300A-II powering the 030s and soon bia-amped with Crown VFX-2A and a D150A-II, I'm not sure that I don't have ample watts to "waste" to heat. These can play plenty loud for as long as you want just with the D150A-II---even using the EQ. Sure, they're not subs, but the sound is addictive anyway. I make some adjustments for the room anyway, but most of my EQ work is to compensate for bad mixes. Sad but true. Lowell George and I seem to agree though!